[1,2,3]Triazolo[4,5-h][1,6]naphthyridines and [1,3]oxazolo[5,4-h][1,6]naphthyridines were synthesized with the aim to investigate their photocytotoxic activity. Upon irradiation, oxazolo-naphtapyridines induced light-dependent cell death at nanomolar/low micromolar concentrations (EC50 0.01-6.59 μM). The most photocytotoxic derivative showed very high selectivity and photocytotoxicity indexes (SI = 72-86, PTI>5000), along with a triplet excited state with exceptionally long lifetime (18.0 μs) and high molar absorptivity (29781 ± 180 M-1cm-1 at λmax 315 nm). The light-induced production of ROS promptly induced an unquenchable apoptotic process selectively in tumor cells, with mitochondrial and lysosomal involvement. Altogether, these results demonstrate that the most active compound acts as a promising singlet oxygen sensitizer for biological applications.
Keywords: Photochemiotherapy; Photosensitizing agents; Reactive oxygen species; [1,2,3]Triazolo[4,5-h][1,6]naphthyridines; [1,3]oxazolo[5,4-h][1,6]naphthyridines.
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